Expandable multi-dimensional sound circuit

Abstract

An expandable multi-dimensional sound system has two modes of operation. Prior to the detection of a 20 kHz tone, the system is configured such that input audio panned hard to the left or right will result in the center and surround channels steering down so that the signal is only passed through the left front and right front channels, respectively. Mono information is fed only through the center channel, as the left and right front channels cancel any center channel or mono information. Material panned hard to the surround position steers down the front left and right channels and is only fed to the rear surround channels. No information is fed to the front center channel due to the fact that the signal contains only difference information. Directional steering to the rear channels is still provided in the absence of any hard broadband left or right panning. Upon the detection of a 20 kHz tone, the system is re-configured such that the left and right front channels and the center channel become disabled. The overhead channel becomes enabled, and the surround channels are not attenuated under hard broadband left or right panning conditions. Center information is fed through the overhead channel, while hard left information appears at the left rear channel and hard right information appears at the right rear channel. Upon the detection of a second 20 kHz tone, the system reverts back to its original operating configuration.

What is claimed is: 
     
       1. A circuit for decoding two input channel stereo signals into multi-channel sound signals comprising: at least one means for combining the two channel stereo signals to provide at least a third input signal;   means for receiving the two input signals and said third input signal and for generating a plurality of steering voltages, each said steering voltage being indicative of a predominance of a respective one of said two input signals and third input signal in one of a plurality of frequency bands;   a plurality of steering means, each for receiving at least one of the two input signals and said third input signal and for providing an output signal derived from its respective at least one of the two input signals and said third input signal attenuated by at least one of said steering voltages; and   at least one means for detecting a signal representative of a tone embedded in said third input signal and for reconfiguring said plurality of steering means in response to detection of said embedded tone signal.   
     
     
       2. A circuit for decoding two channel stereo signals into multi-channel sound signals comprising: means for summing the two channel stereo signals to provide a third signal;   means for differencing the two channel stereo signals to provide a fourth signal;   means for receiving said four signals and for generating a plurality of steering voltages, each said steering voltage being indicative of a predominance of a respective one of said four signals in one of a plurality of frequency bands;   at least one means for receiving said fourth signal and for detecting a signal representative of a tone embedded in at least one of said four signals;   at least one means responsive to said at least one detecting means to generate an override signal for reconfiguring said plurality of steering means in response to detection of said embedded tone signal;   first steering means for receiving said two channel stereo signals and for producing at a first channel an output signal derived therefrom and attenuated by a first of said steering voltages indicative of predominantly third signal information to remove a component desired at a second channel from said first channel output signal and attenuated by a combination of a second of said steering voltages indicative of predominantly fourth signal information and said override signal to remove a component desired at a third channel from said first channel output signal;   second steering means for receiving said two channel stereo signals and for producing at a fourth channel an output signal derived therefrom and attenuated by said first of said steering voltages indicative of predominantly third signal information to remove a component desired at said second channel from said fourth channel output signal and attenuated by a combination of said second of said steering voltages indicative of predominantly fourth signal information and said override signal to remove a component desired at a fifth channel from said fourth channel output signal;   third steering means for receiving said summed third signal and for producing at said second channel an output signal derived therefrom and attenuated by a combination of a third of said steering voltages indicative of predominantly first and second signal broadband information and said override signal;   fourth steering means for receiving said summed third signal and for producing at a sixth channel an output signal derived therefrom and attenuated by a combination of said third of said steering voltages indicative of predominantly first and second signal broadband information and said override signal; and   fifth steering means for receiving said differenced fourth signal and for producing at said third channel an output signal containing a combination of high frequency band second signal and low frequency band first signal information and at said fifth channel an output signal containing a combination of high frequency band first signal and low frequency band second signal information selectively attenuated in response to a switching means operated in response to said override signal by said third steering signal, said third channel output signal being further attenuated by a fourth of said steering voltages indicative of predominantly second signal high frequency band information and by a fifth of said steering voltages indicative of predominantly second signal low frequency band information and said fifth channel output signal being further attenuated by a sixth of said steering voltages indicative of predominantly first signal high frequency band information and by a seventh of said steering voltages indicative of predominantly first signal low frequency band information.